1. Field of the Invention
The invention relates to genetic factors associated with sensitivity to chemotherapeutic drugs. More particularly, the invention relates to methods for identifying such factors as well as to uses for such factors. The invention specifically provides genetic suppressor elements derived from mammalian kinesin genes, and therapeutic and diagnostic uses related thereto.
2. Summary of the Related Art
A broad variety of chemotherapeutic agents are used in the treatment of human cancer. For example the textbook CANCER: Principles & Practice of Oncology, 2d Edition, (De Vita et al., eds.), J.B. Lippincott Company, Philadelphia, Pa. (1985) discloses as major antineoplastic agents the plant alkaloids vincristine, vinblastine, and vindesine; the antibiotics actinomycin-D, doxorubicin, daunorubicin, mithramycin, mitomycin C and bleomycin; the antimetabolites methotrexate, 5-fluorouracil, 5-fluorodeoxyuridine, 6-mercaptopurine, 6-thioguanine, cytosine arabinoside, 5-aza-cytidine and hydroxyurea; the alkylating agents cyclophosphamide, melphalan, busulfan, CCNU, MeCCNU, BCNU, streptozotocin, chlorambucil, bis-diaminedichloro-platinum, azetidinylbenzoquinone; and the miscellaneous agents dacarbazine, mAMSA and mitoxantrone.
These and other chemotherapeutic agents such as etoposide and amsacrine have proven to be very useful in the treatment of cancer. Unfortunately, some tumor cells become resistant to specific chemotherapeutic agents, in some instances even to multiple chemotherapeutic agents. Such drug resistance or multiple drug resistance can theoretically arise from either the presence of genetic factors that confer resistance to the drugs, or from the absence of genetic factors that confer sensitivity to the drugs. The former type of factors have been identified, and include the multiple drug resistance gene mdr-1 (see Chen et al., 1986, Cell 47: 381-389). However, the latter type of factor remains largely unknown, perhaps in part because the absence of such factors would tend to be a recessive trait.
Identification of genes associated with sensitivity to chemotherapeutic agents is desirable, because the discovery of such genes can lead to both diagnostic and therapeutic approaches for cancer cells and for drug resistant cancer cells, as well as to improvements in gene therapy and rational drug design. Recently, some developments have been made in the difficult area of isolating recessive genetic elements, including those involved in cytotoxic drug sensitivity. Roninson et al., U.S. Pat. No. 5,217,889 (issued Jun. 8, 1993) teach a generalized method for obtaining genetic suppressor elements (GSEs), which are dominant negative factors that confer the recessive-type phenotype for the gene to which the particular GSE corresponds. (See also Holzmayer et al., 1992, Nucleic Acids Res. 20: 711-717). Gudkov et al., 1993, Proc. Natl. Acad. Sci. USA 90: 3231-3235 teach isolation of GSEs from topoisomerase II cDNA that induce resistance to topoisomerase II-interactive drugs. Co-pending U.S. patent application Ser. No. 08/033,986, filed Mar. 3, 1993, discloses the discovery by the present inventors of a novel and unexpected result of experiments performed to identify GSEs isolated from RNA of cells resistant to the anticancer DNA damaging agent, etoposide. This reference discloses that a GSE encoding an antisense RNA homologous to a portion of a mouse kinesin heavy chain gene has the capacity to confer etoposide resistance to cells expressing the GSE. The experiments described in this reference also demonstrate that under-expression of the particular kinesin heavy chain gene disclosed therein was associated with naturally-occurring etoposide resistance in cultures of drug-selected human adenocarcinoma cells. These results were particularly unexpected because the role of kinesin genes in etoposide resistance was unknown in the art prior to the instant inventors' discoveries.
The kinesins comprise a family of motor proteins involved in intracellular movement of vesicles or macromolecules along microtubules in eukaryotic cells (see Vale, 1987, Ann. Rev. Cell Biol. 3: 347-378; and Endow, 1991, Trends Biochem. Sci. 16: 221-225 for reviews). Among the family of kinesin genes are encoded kinesin light chains and kinesin heavy chains that assemble to form mature kinesin. A number of kinesin genes have been isolated in the prior art.
Gauger and Goldstein, 1993, J. Biol. Chem. 268: 13657-13666 disclose cloning and sequencing of a Drosophila kinesin light chain gene.
Navone et al., 1992, J. Cell. Biol. 117: 1263-1275 disclose cloning and sequencing of a human kinesin heavy chain gene.
Kato, 1991, J. Neurosci. 2: 704-711 disclose cloning and sequencing of a mouse kinesin heavy chain gene.
Cyr et al., 1991, Proc. Natl. Acad. Sci. USA 88: 10114-10118 disclose cloning and sequencing of a rat kinesin light chain gene.
McDonald & Goldstein, 1990, Cell 61: 991-1000 disclose isolation of a Drosophila kinesin heavy chain gene.
Kosik et al., 1990, J. Biol. Chem. 265: 3278-3283 disclose isolation of a squid kinesin heavy chain gene.
The present inventors have demonstrated that a heretofore unexpected gene, a kinesin heavy chain gene, is involved in cellular sensitivity to the anticancer drug etoposide, and that down-regulation of functional expression of this kinesin heavy chain gene is associated with resistance to this drug. Further experiments, disclosed herein, have suggested that the role of kinesin genes in chemotherapeutic drug resistance may not be limited to this single member of the kinesin gene family. These results further underscore the power of the GSE technology developed by these inventors to elucidate unexpected mechanisms of drug resistance in cancer cells, thereby providing the opportunity and the means for overcoming drug resistance in cancer patients. Reagents and methods directed towards such goals are provided in this disclosure.